Comonomer compositions for production of imide-containing polyamino acids

ABSTRACT

Described are monomer compositions containing aspartic acid and other comonomers, such as monosodium aspartate, and methods for their production. The monomer compositions can be polymerized, particularly by thermal polymerization, to obtain useful and novel imide-containing polyamino acids, i.e., copolymers containing polymerized aspartate units and succinimide units. The invention is also directed to the resulting polymeric materials, their methods of production, and their uses. Uses of the imide-containing polyamino acids include, for example, dispersants in detergents and cleansers, water-treatment chemicals as anti-scalants and corrosion inhibitors, personal-care additives for softening and moisturizing, and many others.

The present invention includes monomer compositions containing asparticacid and other comonomers, such as monosodium aspartate, and methods fortheir production. The monomer compositions can be polymerized,particularly by thermal polymerization, to obtain useful and novelimide-containing polyamino acids, i.e., copolymers containingpolymerized aspartic acid or aspartate units and succinimide units.Thus, the invention is also directed to the resulting polymericmaterials, their methods of production, and their uses as describedherein. Uses of the imide-containing polyamino acids include, forexample, dispersants in detergents and cleansers, water-treatmentchemicals as anti-scalants and corrosion inhibitors, personal-careadditives for softening and moisturizing, and many others.

BACKGROUND OF THE INVENTION

Aspartic acid has been produced commercially since the 1980's viaimmobilized enzyme methods. The aspartic acid so produced mainly hasbeen used as a component of the synthetic sweetener, N-aspartylphenylalanine methyl ester (ASPARTAME®).

In a typical production pathway, a solution of ammonium maleate isconverted to fumarate via action of an immobilized enzyme, maleateisomerase, by continuous flow over an immobilized enzyme bed. Next, thesolution of ammonium fumarate is treated also by continuous flow of thesolution over a bed of the immobilized enzyme, aspartase. A relativelyconcentrated solution of ammonium aspartate is produced, which then istreated with an acid, for example nitric acid, to precipitate asparticacid. After drying, the resultant product of the process is powdered orcrystalline L-aspartic acid. Prior art that exemplifies this productionpathway includes U.S. Pat. No. 4,560,653 to Sherwin and Blouin (1985),U.S. Pat. No. 5,541,090 to Sakano et al. (1996), and U.S. Pat. No.5,741,681 to Kato et al. (1998).

In addition, nonenzymatic, chemical routes to D,L aspartic acid viatreatment of maleic acid, fumaric acid, or their mixtures with ammoniaat elevated temperature have been known for over 150 years (see Harada,K., Polycondensation of thermal precursors of aspartic acid. Journal ofOrganic Chemistry 24, 1662-1666 (1959); also, U.S. Pat. No. 5,872,285 toMazo et al. (1999)). Although the nonenzymatic routes are significantlyless quantitative than the enzymatic syntheses of aspartic acid,possibilities for continuous processes and recycling of reactants andby-products via chemical routes are envisioned.

Polymerization and copolymerization of aspartic acid alone or with othercomonomers is known. As reviewed in U.S. Pat. No. 5,981,691 to Sikes(1999), synthetic work with polyamino acids, beginning with thehomopolymer of aspartic acid, dates to the mid 1800's and has continuedto the present. Interest in polyaspartates and related moleculesincreased in the mid 1980's as awareness of the commercial potential ofthese molecules grew. Particular attention has been paid tobiodegradable and environmentally compatible polyaspartates forcommodity uses such as detergent additives and superabsorbent materialsin disposable diapers, although numerous other uses have beencontemplated, ranging from water-treatment additives for control ofscale and corrosion to anti-tartar agents in toothpastes.

There have been some teachings of producing copolymers of succinimideand aspartic acid or aspartate via thermal polymerization of maleic acidplus ammonia or ammonia compounds. For example, U.S. Pat. No. 5,548,036to Kroner et al.(1996) taught that polymerization at less than 140° C.resulted in aspartic acid residue-containing polysuccinimides. However,the reason that some aspartic acid residues persisted in the productpolymers was that the temperatures of polymerization were too low todrive the reaction to completion, leading to inefficient processes.

JP 8277329 (1996) to Tomida exemplified the thermal polymerization ofpotassium aspartate in the presence of 5 mole % and 30 mole % phosphoricacid. The purpose of the phosphoric acid was stated to serve as acatalyst so that molecules of higher molecular weight might be produced.However, the products of the reaction were of lower molecular weightthan were produced in the absence of the phosphoric acid, indicatingthat there was no catalytic effect. There was no mention of producingcopolymers of aspartate and succinimide; rather, there was mention ofproducing only homopolymers of polyaspartate. In fact, addition ofphosphoric acid in this fashion to form a slurry or intimate mixturewith the powder of potassium aspartate, is actually counterproductive toformation of copolymers containing succinimide and aspartic acid residueunits, or to formation of the condensation amide bonds of the polymersin general. That is, although the phosphoric acid may act to generatesome fraction of residues as aspartic acid, it also results in theoccurrence of substantial amounts of phosphate anion in the slurry ormixture. Upon drying to form the salt of the intimate mixture, suchanions bind ionically with the positively charged amine groups ofaspartic acid and aspartate residues, blocking them from thepolymerization reaction, thus resulting in polymers of lower molecularweight in lower yield.

Earlier, U.S. Pat. No. 5,371,180 to Groth et al. (1994) had demonstratedproduction of copolymers of succinimide and aspartate by thermaltreatment of maleic acid plus ammonium compounds in the presence ofalkaline carbonates. The invention involved an alkaline, ring-openingenvironment of polymerization such that some of the polymericsuccinimide residues would be converted to the ring-opened, aspartateform. For this reason, only alkaline carbonates were taught and therewas no mention of cations functioning themselves in any way to preventimide formation.

More recently, U.S. Pat. No. 5,936,121 to Gelosa et al. (1999) taughtformation of oligomers (Mw<1000) of aspartate having chain-terminatingresidues of unsaturated dicarboxylic compounds such as maleic andacrylic acids. These aspartic-rich compounds were formed via thermalcondensation of mixtures of sodium salts of maleic acid plusammonium/sodium maleic salts that were dried from solutions of ammoniummaleate to which NaOH had been added. They were producing compounds tosequester alkaline-earth metals. In addition, the compounds were shownto be nontoxic and biodegradable by virtue of their aspartic acidcomposition. Moreover, the compounds retained their biodegradability byvirtue of their very low Mw, notwithstanding the presence of thechain-terminating residues, which when polymerized with themselves tosizes above the oligomeric size, resulted in non-degradable polymers.

A number of reports and patents in the area of polyaspartics (i.e.,poly(aspartic acid) or polyaspartate), polysuccinimides, and theirderivatives have appeared more recently. Notable among these, forexample, there have been disclosures of novel superabsorbents (U.S. Pat.No. 5,955,549 to Chang and Swift, 1999; U.S. Pat. No. 6,027,804 to Chouet al., 2000), dye-leveling agents for textiles (U.S. Pat. No. 5,902,357to Riegels et al., 1999), and solvent-free synthesis ofsulfhydryl-containing corrosion and scale inhibitors (EP 0 980 883 toOda, 2000). There also has been teaching of dye-transfer inhibitorsprepared by nucleophilic addition of amino compounds to polysuccinimidesuspended in water (U.S. Pat. No. 5,639,832 to Kroner et al., 1997),which reactions are inefficient due to the marked insolubility ofpolysuccinimide in water.

U.S. Pat. No. 5,981,691 purportedly introduced the concept of mixedamide/imide, water-soluble copolymers of aspartate and succinimide for avariety of uses. The concept therein was that a monocationic salt ofaspartate when formed into a dry mixture with aspartic acid could bethermally polymerized to produce the water-soluble copoly(aspartate,succinimide). The theory was that the aspartic acid comonomer whenpolymerized led to succinimide residues in the product polymer and themonosodium aspartate comonomer led to aspartate residues in the productpolymer. It was not recognized that merely providing the comonomers wasnot sufficient to obtain true copolymers and that certain otherconditions were necessary to avoid obtaining primarily mixtures ofpolyaspartate and polysuccinimide copolymers. In U.S. Pat. No.5,981,691, the comonomeric mixtures were formed from an aqueous slurryof aspartic acid, adjusted to specific values of pH, followed by drying.There was no teaching of use of solutions of ammonium aspartate or anyother decomposable cation plus NaOH, or other forms of sodium or othercations, for generation of comonomeric compositions of aspartic acid andsalts of aspartate. Thus, although some of the U.S. Pat. No. 5,981,691examples obtain products containing some copolymer in mixture with otherproducts, particularly homopolymers, as discussed in the Summary of theInvention below, the theory that true copolymers could be obtainedmerely by providing the comonomers in the manner taught in U.S. Pat. No.5,981,691 was not fully realized.

Thus, to date, there have been no successful disclosures ofwater-soluble or wettable, mixed amide/imide polyamino acids such ascopolymers of aspartate and succinimide or related imide-containingpolyamino acids.

SUMMARY OF THE INVENTION

It has now been discovered that the methods taught in U.S. Pat. No.5,981,691, or in any of the other discussed references, fail to providean efficient process to produce a true mixed amide/imide polyamino acidcopolymer, a copolymer prepared by such process or other novelcopolymers. These previous references fail to teach a method whereby asufficiently intimate mixture of the comonomers is provided such thatpolymerization leads to a true copolymer with a significant number ofboth aspartate and succinimide residues. For example, theabove-described method of U.S. Pat. No. 5,981,691 purportedly forproducing such copolymers results, instead in a mixture, albeit intimatemixture, of aspartic acid (amide) and succinimide (imide) homopolymers,possibly with an amount of copolymer, unappreciated by the reference,mixed therein. A method has now been discovered providing a sufficientlyintimate mixture of the comonomers and, therefore, allowing theproduction of a true copolymer with a significant number of bothaspartate (also referred to as amide) residues or units and succinimide(also referred to as imide) units or residues, as schematically shown bythe following formula.

The invention also can provide the resulting copolymers in isolatedform. By isolated form it is meant that the copolymer is either: (a) inthe substantial absence, e.g., less than 10%, preferably less than 5%,more particularly less than 1%, by weight of a polyaspartate orpolysuccinimide homopolymer, (b) prepared by a method defined by thisinvention or (c) prepared by some other method not of this invention butwhich has a step of separating polyaspartate and/or polysuccinimidehomopolymer from the copolymer.

Accordingly, the present invention teaches novel methods for producingmixed amide/imide copolymers of amino acids, as well as the resultingnovel imide-containing polyamino acids themselves. Included are methodsemploying the monomers aspartic acid or aspartate salts havingnon-volatile or non-heat-decomposable cations. By aspartate or aspartatesalt is meant a salt of the aspartate ion and any metallic cation,including alkali metal, alkaline earth metals or transition metals.Preferably the cations are alkali or alkaline earth metals, particularlyNa, Mg, K, Ca, Rb, Sr, Cs and Ba, with sodium, magnesium, potassium andcalcium, particularly sodium, being preferred. These monomers lead toamide formation. Other monomer, particularly aspartates having avolatile or heat-decomposable cation, preferably an ammonium or aminecation, lead to imide formation. In the following, the amide-generatingcation will be represented by sodium (Na⁺) and the imide-generatingcation will be represented by ammonium (NH₄ ⁺) but with theunderstanding that other cations creating the same effects for achievingthe invention may be substituted. By volatile or heat-decomposablecation it is meant that the cation sufficiently dissociates from theaspartate anion under the giving drying conditions such that theremaining aspartate unit can cyclize to a succinimide unit during thepolymerization. Cations which have at least 50% dissociation in thismanner under the given drying conditions are considered volatile orheat-decomposable and cations which do not dissociate at least 50% areconsidered non-volatile or non-heat-decomposable.

In the present invention, some elements of the conventional, enzymaticprocesses for production of aspartic acid can be adapted for producingmonomers useful in the invention. The production of the comonomermixture, however, is a novel aspect. The method involves providing anintimate solution of an aspartate of a non-volatile cation and anaspartate of a volatile cation. By the term aspartate is meant anaspartic acid residue, either as a monomer or as a polymerized orcopolymerized unit having its carboxyl group in ionic form associatedwith a cation, i.e., as —COO⁻. Specifically, for example, an ammoniumaspartate solution can be titrated with NaOH to a fractional molarequivalence of a sodium salt of aspartate and an ammonium salt ofaspartate. This comonomeric solution is then dried to produce acomonomer mixture of a partial sodium salt of aspartic acid and freeaspartic acid. By free aspartic acid is meant aspartic acid or apolymerized or copolymerized aspartic acid residue having its carboxylgroup not in ionic form, i.e., as —COOH. Because the dried comonomermixture is prepared from the novel intimate solution of comonomers, anintimate dried mixture of these comonomers is obtained. Although notintending to be bound by this theory, it is believed that the mixture isintimate to the extent of exhibiting a salt lattice structure of theaspartate with the aspartic acid. It is possible for the driedcomonomeric composition to also contain some residual ammoniumaspartate, but in very small amounts, e.g., not exceeding 5% by weight,preferably not exceeding 2% by weight.

In effect, the aspartate of the volatile cation (e.g., ammonium) whendried from aqueous solution, is largely converted to powdered orcrystalline aspartic acid. This is due to the loss of the decomposablecation, e.g., ammonia, as a vapor upon drying, with accompanyinglowering of the pH of the evaporating solution as ammonia leaves thesolution, for example, as a result of the following equilibrium beingpulled to the left:

↑NH₃⇄NH₃+H₂O⇄NH₄OH⇄NH₄ ⁺¹+OH⁻.

The sodium ion, on the other hand, has no significant vapor phase duringdrying and remains in the dried salt as a counter ion to aspartatemonomers. Thus, the relative proportions of the comonomers, monosodiumaspartate and aspartic acid, is set by the relative molar amounts ofammonium aspartate in solution and the NaOH added to the solution priorto drying.

The dried comonomer mixture is a clear, glassy solid if drying occurs invacuo or in an oxygen-depleted atmosphere. In the presence ofatmospheric oxygen, the dried comonomer preparation has a pale yellow,glassy appearance.

The comonomer composition of the present invention may also be preparedvia nonenzymatic, chemical production of solutions of ammoniumaspartate. For example, maleic acid plus ammonia in water plus heating,preferably at an elevated pressure, may produce ammonium aspartate insolution. Typically, temperatures of 80 to 160° C., preferably 120 to160° C. and a pressure of up to about 120 psi can be used, althoughother conditions may be useful depending on the particularcircumstances. Upon addition of the desired amount of NaOH, thissolution is dried to form the comonomer composition containing themixture of the sodium aspartate salt and aspartic acid.

The comonomeric composition may also be obtained via coprecipitationfrom solution. For example, addition of a hydrophobe or downwardadjustment of pH may lead to coprecipitation of the monomers. These maythen be isolated, for example by filtration, for use in the productionof the imide-containing polymers.

Also included are methods in which maleic acid plus ammonia plussoluble, nonalkali as well as alkali, cationic salts are used tointernally generate a combination of aspartic acid and monosodiumaspartate comonomers for thermal polymerization to producewater-soluble, imide containing copolymers.

Upon polymerization, for example by thermal polycondensation, of thecomonomer composition, any residual ammonia of the ammonium salt isfurther driven off as a vapor. The resulting product is a copolymer ofsodium aspartate and succinimide units. Due to the novel comonomer drymixture used to prepare this copolymer, a true copolymer is obtainedwith a significant amount of both of these amide and imide units. Forexample, it is preferred that such units are provided in the copolymerin a molar ratio of from 1:10 to 10: 1, more preferably 1:5 to 5:1,particularly preferably 1:4 to 4:1 or at about 1:1. Exemplification ofthe ratios achievable is provided in the following Table 1.

TABLE 1 Titratable COOH groups of copolymers of aspartate andsuccinimide; the higher number of titratable COOH groups beingindicative of a higher ration of aspartate units. Titratable COOHGroups; μmoles-COOH per milligram of polymer Actual Material Theoretical(n = ≧ 4 ± st. dev.) Polysuccinimide <1.00 1.30 Mono Na polyaspartate7.25 6.22 Copoly(asp:suc) 5:1 6.04 6.22 ± 0.21  Copoly(asp:suc) 4:1 5.805.41 ± 0.099 Copoly(asp:suc) 3:1 5.43 5.23 ± 0.188 Copoly(asp:suc) 2:14.78 4.80 ± 0.151 Copoly(asp:suc) 1:1 3.62 3.52 ± 0.116 Copoly(asp:suc)1:2 2.51 2.66 ± 0.100 Copoly(asp:suc) 1:3 1.81 2.07 ± 0.051Copoly(asp:suc) 1:4 1.45 1.72 ± 0.014

These copolymers exhibit advantageous properties, particularlyadvantageous water solubility properties, which makes them economicallyand ecologically advantageous for use in many applications. For example,they can provide biodegradeable polymers and polymers which canotherwise be adjusted to suit particular uses. Table 2 exemplifies someof the advantageous solubility properties of copolymers of theinvention:

TABLE 2 SOLUBILITY IN 50% AQUEOUS MATERIAL¹ SOLUBILITY IN H₂OISOPROPANOL Copoly (asp:suc) 1:1   90%² 2.5% Copoly (asp:suc) 1:2 <30% <2.5%  Copoly (asp:suc) 2:1 90% 2.5% Copoly (asp:suc) 3:1 90% 2.5%Copoly (asp:suc) 1:3 <5% Not Soluble Copoly (asp:suc) 4:1 90% 2.5%Copoly (asp:suc) 1:4 <5% Not Soluble Copoly (asp:suc) 5:1 In aqueousalcoholic liquid laundry formulation³: >5.0% ¹Copolymers prepared at200° C., 4 hours. ²Weight/volume ³Liquid Tide

Additional comonomers may be added prior to the drying of the comonomersolution step to provide comonomeric feedstock for terpolymers andhigher polymers of thermally condensed polyamino acids. In particular,the amino acids lysine and glutamate and salts thereof may be used.These can impart further water-solubility to the productimide-containing polymers. Moreover, other difunctional andmultifunctional monomers such as aminocaproic acid and ornithine, aswell as the other common amino acids including but not limited toalanine, glycine, leucine, isoleucine, methionine, and threonine;sugar-acids such as glucuronic acid; other hydroxyl-containingcarboxylates such as citric acid and malonic acid; and other likemolecules, are additional comonomers that would co-condense in theproduction of the imide-containing polyamino acids and may be useful toprovide aqueous solubility and other useful properties to theimide-containing polyamino acids.

Accordingly, it is one object of the present invention to provide novelcomonomeric compositions. It is another object of the present inventionto provide methods of preparation of the novel comonomeric compositions.It is another object of the present invention to provide uses of thenovel comonomeric compositions, particularly for copolymerization toprepare novel copolymers. It is another object of the present inventionto provide novel imide-containing polyamino acids. It is another objectof the present invention to provide methods of synthesis of theimide-containing polyamino acids. It is another object of the presentinvention to provide methods of commercial manufacture of theimide-containing polyamino acids. It is another object of the presentinvention to provide methods of using, including commercial uses, of theimide-containing polyamino acids. This exemplification of objects of theinvention is not a limitation and other objects and advantages of theinvention are either explicitly or implicitly included in the disclosureas a whole, taking the knowledge of one of ordinary skill in the artinto consideration.

Comonomeric Compositions. The comonomeric compositions of the presentinvention can be prepared via the intimate solutions described above.

To prepare the starting solutions of aspartic acid and/or ammoniumaspartate any current commercial process may be used. For example, driedpowders or crystals of L-aspartic acid may be prepared byacid-precipitation of ammonium aspartate solutions such as occur as anintermediate stage of the immobilized enzyme route to aspartic acid.

Alternatively, aspartic acid for use in the present invention may beprepared chemically via addition of ammonia to maleic acid or fumaricacid plus heat, followed by acid precipitation of the aspartic acidzwitterion. Accordingly, either L-aspartic acid or D-aspartic acid maybe used, or mixtures of L,D-aspartic acid may be used in this invention.

A novel and preferred method of preparation of the composition ofcomonomeric salts of the present invention is to add alkali to aconcentrated solution of ammonium aspartate, where the solution ofammonium aspartate is prepared by any of the prior routes for productionof aspartic acid. Specifically, stoichiometric, substoichiometric, orsuprastoichiometric amounts of one or more alkali compounds relative tothe molar amounts of ammonium aspartate, either diammonium ormonoammonium, may be added. The solutions are then dried by any method,preferably at a temperature of from 80 to 140° C., more preferablyoven-dried at 120° C., to form the partial sodium salt of aspartate andaspartic acid, although residual ammonium aspartate may also be present.Drying could also be conducted by spray drying, lyophilization, vacuummethods or forced air. The drying can be halted at a time beforepolymerization of the comonomers begins. However, it is also possible tocontinue the drying step after the comonomers are formed to proceed withthe copolymerization thereof, as discussed below, in situ.

During the drying step, the ammonia is largely released to theatmosphere, which ammonia gas may be scrubbed by passage through anacidified, cool-water trap. The ammonium aspartate thus reverts to theaspartic acid form. The sodium hydroxide acts to neutralize some of theaspartic acid upon drying. The sodium ion, having no significant vaporpressure, remains in the comonomeric salt composition of the presentinvention in the form of monosodium aspartate.

If the drying step is accomplished with heating in vacuo, bylyophilization, or with heating in an inert, oxygen-depleted atmospheresuch as nitrogen gas, the resultant comonomeric salt of the presentinvention is a colorless, clear, glassy solid that may be obtained invarious forms ranging from a solid puck to glassy particles to shards topowders.

Another preferred method of preparation of the comonomeric salts of thepresent invention is to mix stoichiometric, substoichiometric, orsuprastoichiometric solutions of sodium aspartate with a solution ofammonium aspartate. For example, dry or powdered aspartic acid may besolubilized by titration with a minimal amount of NaOH, just sufficientto render the aspartic acid into solution. Alternatively, the NaOH maybe added in an excess, for example sufficient to provide two sodium ionsper molecule of aspartic acid. Next, the two solutions are mixed, withaddition of enough of one with the other to provide a combined solutioncontaining the targeted molar ratio of ammonium versus sodium aspartate,in either case either the di- or monoammonium or di- or monosodiumsalts. The drying is then conducted as described above or by any otherconventional means, leaving the resulting comonomer preparation of thepresent invention.

In any of the above methods the amounts of the aspartic acid andaspartate salts used are provided to reflect the desired ratio of amideand imide units in the eventual copolymer. The desired ratio may beselected based on the properties desired, e.g., a higher ratio of amide(aspartate) units in the copolymer will provide it greater solubility.Thus, e.g., a molar ratio of from 1:10 to 10:1, more preferably 1:4 to4:1, particularly about 1:1, may be used.

The amide-generating or imide-generating monomers are not limited toones having sodium and ammonium cations, respectively; other cations maybe used in a manner analogous to that described above. As theamide-generating cations may be used those which form aspartate saltswherein the cation is non-volatile or not heat decomposable under theconditions for drying to the comonomer mixture. Preferred, therefore,are cations which exhibit no significant vapor pressure at 120° C.Representative examples include any metallic cation, such as alkalimetal, alkaline earth metals or transition metals. Preferably thecations are alkali or alkaline earth metals, particularly Na, Mg, K, Ca,Rb, Sr, Cs and Ba, with sodium, magnesium, potassium and calcium,particularly sodium, being preferred alkali metals and alkaline earthmetals. As the imide-generating cations may be used those which formaspartate salts which are volatile or heat decomposable under theconditions for drying to the comonomer mixture. Preferred, therefore,are cations that volatilize or are otherwise dissipated at 120° C.Representative examples include ammonium and other amines which providecounterions to aspartate carboxylic groups in solution, e.g.,ethanolamine, propanolamine and monoaminobutane.

Comonomers in addition to the amide-generating and imide-generatingaspartates may be used in the preparation of comonomer compositions forthe production of imide-containing polyamino acids, and analogousmethods to those described above using such other monomers are includedin the invention. Use of such additional comonomers results interpolymers or higher polymers. These further comonomers may be selectedfrom among any comonomers which copolymerize and do not interfere withformation of the amide/imide copolymer units. Many useful comonomers areconventionally known and are included here, for example, other aminoacids, e.g., any natural or modified amino acids as long as they containat least one amino group and at least one carboxylic group free forpolymerization and salts thereof.

The amount of the additional comonomer used is preferably in the rangeof 10 to 50% weight based on the total weight of the amide- andimide-generating comonomers.

An example of an additional comonomer is monosodium glutamate.Monosodium glutamate in dry form or as a solution may be added to asolution of ammonium aspartate, mixed to make a combined solution, thendried by any conventional means to produce a dried comonomer compositionof aspartic acid and monosodium glutamate. The composition may alsocontain sodium aspartate, glutamic acid, or a combination of thesecomonomers.

Another preferred comonomer is lysine. Lysine, most preferably as thefree base, and preferably having few or no counterions, such aschloride, associated with the amine groups of lysine, may be added indry form or as a solution to a solution of ammonium aspartate, mixed tomake a combined solution, then dried by any conventional means toproduce a dried comonomer composition of aspartic acid and lysine. Thecomposition may also contain sodium aspartate, glutamic acid, sodiumglutamate, or a combination of these comonomers. Lysine may also beadded as the chloride salt, lysine-HCl, but this is not particularlypreferred, as the chloride may form counterions with free amino groupsof the amino acids upon drying, blocking them from participating in thethermal polycondensation reaction to form the ultimate products, theimide-containing polyamino acids.

Lysine in the free-base form, which is prepared commercially as thezwitterion, when incorporated into the comonomer composition of thepresent invention, acts to extend the molecular size of theimide-containing polyamino acid products, presumably throughchain-extension and crosslinking. Similarly, other diamino or polyaminomonomeric coreactants may be used for this purpose. For example,ornithine may be used, as may aminocaproic acid, diaaminohexane,diaminobutane and diaminopentane.

In all cases, the L-, D-, or mixed L-,D- isomers of the monomeric aminoacids and other comonomers may be used.

In a separate embodiment for providing a comonomer mixture useful forobtaining imide-containing polyamino acids, sodium bicarbonate or othercarbonate ion-providing compounds can be used. The water of condensationcreates a vapor phase during the polymerization of aspartic acid. In thepresence of sodium bicarbonate, bicarbonate anion can enter a transitoryaqueous state, with sodium cation also solubilized momentarily. Thebicarbonate decomposes in the presence of heat and water vapor torelease CO₂ and water, further stirring the admixture through gaseousemission. The sodium can become a counterion to some of the asparticresidues in the form of monosodium aspartate, thus generating anintimate mixture of aspartic acid and monosodium aspartate comonomers.Upon thermal polymerization, this intimate mixture converts to thecopolymer of aspartate and succinimide as further discussed below.

Manufacture of the Imide-containing Polyamino Acids. The novel polymericmolecules of the present invention may be produced via methods analogousto those described in the prior art for manufacture, includingcommercial manufacture, of the homopolymers, polysuccinimide andpolyaspartate, except of course using the comonomer compositionsaccording to the invention. Accordingly, the molecules of the presentinvention may be manufactured by the approaches exemplified in Table 3,which includes relevant prior art references, incorporated herein intheir entirety by reference. In one preferred embodiment, the comonomermixture is heated by a thermal polycondensation method. Although thepolymerization time and temperature will depend on the comonomer mixtureused and the result desired, the polymerization can preferably beconducted at a temperature of from 140 to 350° C., more preferably 160to 280° C., particularly 200 to 240° C., for preferably 1 minute to 72hours, more preferably 5 minutes to 8 hours, to form the copolymers. Inone embodiment of the preparation, a thin film evaporator may be used toprovide a short time (e.g., as little as 5 minutes) for completeconversion of the monomers to the polymer due to the efficiency of heatexchange and removal of water of condensation.

The copolymers may be formed in a large range of molecular weights. Inone embodiment, the copolymers may exhibit a gel permeation molecularweight of from 300 to 5,000 daltons, particularly 500 to 3,000 daltons.A higher ratio of succinimide units will generally result in a highermolecular weight copolymer. In other embodiments the copolymer may bepolymerized to an extent to provide a molecular weight of 100,000 orhigher. The molecular weight of the copolymer may be increased byincluding a polyamine (including diamines) as an additional comonomer;see the description regarding comonomers above. Suitable diamines andpolyamines include aliphatic diamine, arylaliphatic diamines, as will astriamino, tetramino and polyamino compounds, such as polyoxyalkylenetriamine, polyoxyalkylene diamine, triethylene tetraamine andtetraethylene pentamine. Such polyoxyalkylene amines are available, forexample, as JEFFAMINES® from Huntsman Specialty Chemicals and asSTARBURST® dendrimers from Dendritech, Inc. The JEFFAMINES® typicallycontain ethylene and/or propylene oxide units and have molecular weightsranging from 600 to 5000. Preferred polyamines are diaminopropane,diaminobutane, diaminopentane, diaminohexane, diaminoheptane,diaminoctane, omithine, onithine methyl ester, lysine, lysine methylester, spermine and spermidine. Particularly preferred diamines includediaminobutane, diaminopropane, diaminohexane and lysine methyl ester.

Typically, the polyamine is incorporated in a monomer mixture ofpolyamine and monosodium aspartate in an amount of 1 to 50 mole %,preferably 5 to 15 mole %, based on the total moles of polyamine andsalt of aspartic acid in the monomer mixture. By including a polyaminein the monomer mixture it is possible to increase the molecular weightof the resulting poly(aspartate,succinimide) to 100,000 daltons andhigher as measured by gel permeation.

In another embodiment, the present method may be carried out bypolymerizing the comonomer mixture of the invention in the presence of apreformed polyaspartate. The preformed polyaspartate may be thatprepared by a process analogous to that described in U.S. Pat. No.5,981,691 or that prepared by some other conventional polymerization ofaspartic acid or aspartates followed by hydrolysis. Typically, thepreformed polyaspartate will have a gel permeation molecular weight of1000 to 100,000, preferably 2000 to 30,000 daltons. The preformedpolyaspartate is usually included in the polymerization in an amount of25 to 95 mole % preferably 50 to 90 mole %, based on the total moles ofresidues (monomer units) of the copolymer.

By the use of preformed polyaspartates or by other methods, copolymersaccording to the invention can be provided having at least a partiallyblock copolymer structure. Additionally, graft copolymers can beprovided according to known methods.

The copolymers of the invention can exhibit a linear structure orbranched structure, including three-dimensional structuring.Crosslinking of the copolymers according to known methods can also beconducted. Also, a variety of terminal groups known in the art can beprovided on the copolymers.

TABLE 3 Some Useful Thermal Manufacturing Processes For the Polymers Ofthe Present Invention, Including Prior Art References Related ToPolyaspartates And Related Materials Thermal Manufacturing ProcessesPatent Number Year Authors Fluidized bed reactor (Littleford) U.S. Pat.No. 5057597 1991 Koskan, L. P. WO 98/34976 1998 Martin, D. A. U.S. Pat.No. 5830985 1998 Kroner, M. et al. Kneading reactor, continuous U.S.Pat. No. 5610255 1997 Groth, T. et al. Microwave Reactor U.S. Pat. No.4696981 1987 Harada, K. et al. Rapidly mixed coreactants in U.S. Pat.No. 5594077 1997 Groth, T. et al. continuous reactors including: U.S.Pat. No. 5919894 1999 Schubart, R. delay tubes high viscosity reactors(screw, List) Driers stirred tank cascades thin layer evaporatorsmulti-phase spiral tubes Mixed coreactants in noncontinuous U.S. Pat.No. 5371180 1997 Groth, T. et al. or continuous reactors including:kneading machines paddle driers screw machines belt driers roller driersTray driers (Wyssmont, Krauss Maffe) U.S. Pat. No. 5319145 1994 Paik, Y.H. et al. U.S. Pat. No. 5401428 1995 Kalota, D. et al. WO 98/34976 1998Martin, D. A. Rotary drier, Plate drier U.S. Pat. No. 5315010 1994Koskan, L. P. et al.

Uses of the Imide-containing Polyamino Acids. The novel molecules of thepresent invention may be used in a manner analogous to that described inthe prior art for possible uses of polysuccinimides and polyaspartates,including described commercial uses. Accordingly, the molecules of thepresent invention, i.e., including the described copolymers of aspartateand succinimide (i.e., the imide-containing polyamino acids) and thederivatives thereof discussed below, may be used as summarized in Table4, which includes the relevant prior art references, incorporated hereinin their entirety by reference.

TABLE 4 Uses of the Polymers of the Present Invention, Including PriorArt References to Uses of Polyaspartates and Related Materials. UsePatent Number Year Authors antifreezes U.S. Pat. No. 5942150 1999 Heuer,L. et al. antiscalants boiler water U.S. Pat. No. 5658464 1997 Hann, W.M. et al. cooling water U.S. Pat. No. 4534881 1985 Sikes, C. S. and A.P. Wheeler U.S. Pat. No. 5658464 1997 Hann, W. M. et al. desalinatorsU.S. Pat. No. 5548036 1996 Kroner, M. et al. fruit/sugar extraction U.S.Pat. No. 5939522 1999 Mazo, G. Y. et al. oilfield EP 0 980 883 A1 2000Oda, Y. U.S. Pat. No. 6022401 2000 Tang, J. et al. reverse osmosismembranes WO 98/22205 A1 1998 Groeschl, A. et al. U.S. Pat. No. 60019561999 Wood, L. L. and G. J. Calton antistatics U.S. Pat. No. 5502251 1996Pohmer, K. et al. JP 08041445 A2 1996 Tamaya, H. et al. adhesives U.S.Pat. No. 5939522 1999 Mazo, G. Y. et al. bioabsorbable medical devicesU.S. Pat. No. 5397816 1995 Reilly, E. P. et al. biological coatingsantiproteolytic, antihydrolytic U.S. Pat. No. 6022860 2000 Engel, J. etal. U.S. Pat. No. 5834273 1998 Futatsugi, M. and Kenji Gushi cationictoxin suppressants U.S. Pat. No. 5498410 1996 Gleich, G. J. cell andtissue encapsulation U.S. Pat. No. 5573934 1996 Hubbell, J. A. et al.cellular adhesion inhibitors U.S. Pat. No. 5573934 1996 Hubbell, J. A.et al. cellular adhesion promoters U.S. Pat. No. 5470843 1995 Stahl, W.et al. U.S. Pat. No. 5395619 1995 Zalipsky, S. et al. coatings for foodmaterials U.S. Pat. No. 5175285 1992 Lehmann, K. et al.immunosuppressants U.S. Pat. No. 5693514 1997 Dorian, R. E. and K. C.Cochrum pharmaceutical carriers U.S. Pat. No. 5578323 1996 Milstein, S.J. and M. L. Kantor blood plasma expanders DE 2032470 1971 Neri, P. etal. botanical additives Herbicide absorption enhancers U.S. Pat. No.5635447 1997 Sanders, J. L. Plant growth enhancers U.S. Pat. No. 57835231998 Koskan, L. P. et al. U.S. Pat. No. 5935909 1999 Sanders, J. L.Plant growth factors U.S. Pat. No. 6022860 2000 Engel, J. et al. Plantfreshness preservatives U.S. Pat. No. 5580840 1996 Harms, D. J. and A.R. Y. Meah carriers of therapeutic agents U.S. Pat. No. 5904936 1999Huille, S. et al. chelants, sequestrants EP 0 826 716 A2 1998 Nakato, T.and M. Tomida U.S. Pat. No. 5936121 1999 Gelosa, D. et al. EP 0 980 883A1 2000 Oda, Y. chromatographic agents U.S. Pat. No. 4517241 1985Alpert, A. J. conditioners U.S. Pat. No. 5925728 1999 Kim, S. et al.controlled release biocides U.S. Pat. No. 5904936 1999 Huille, S. et al.drugs U.S. Pat. No. 5904936 1999 Huille, S. et al. U.S. Pat. No. 60228602000 Engel, J. et al. flavors U.S. Pat. No. 5540927 1996 Jason, M. E.and D. J. Kalota fragrances U.S. Pat. No. 5556835 1996 Inaoka, T. et al.plant growth factors U.S. Pat. No. 5904936 1999 Huille, S. et al.corrosion inhibitors JP 11350172 A 1999 Shokubai, N. EP 0 980 883 A12000 Oda, Y. U.S. Pat. No. 6022401 2000 Tang, J. et al. cosmetics U.S.Pat. No. 4363797 1982 Jacquet, B. et al. U.S. Pat. No. 4735797 1988Grollier, J. and C. Fourcadier detergents and cleansers antiredepositionagents U.S. Pat. No. 5962400 1999 Thomaides, J. S. et al. builders U.S.Pat. No. 6001798 1999 Baur, R. et al. U.S. Pat. No. 5658872 1997 DuVosel, A. et al. color protectants U.S. Pat. No. 6040288 2000 Popoff, C.et al. dye-transfer inhibitors U.S. Pat. No. 5639832 1997 Kroner, M. etal. fragrance retaining aids U.S. Pat. No. 6040288 2000 Popoff, C. etal. liquid laundry dispersants JP 11092787 A 1999 Nippon Shokubaipowdered laundry dispersants U.S. Pat. No. 5266237 1993 Freeman, M. B.et al. U.S. Pat. No. H 1,514 1996 Willman, K. and J. Vandermeer U.S.Pat. No. 5770553 1998 Kroner, M. et al. soil release agents U.S. Pat.No. 5902782 1999 Hall, R. G. and A. D. Willey dispersants cement U.S.Pat. No. 5908885 1999 Sikes, C. S. et al. ceramic and metal particlesU.S. Pat. No. 5328690 1994 Sikes, C. S. U.S. Pat. No. 5503771 1996Staley, J. T. et al. coal U.S. Pat. No. 5548036 1996 Kroner, M. et al.drilling mud U.S. Pat. No. 5552514 1996 Adler, D. E. et al. inks WO97/43351 1997 Krepski, et al. milling EP 0860 477 A1 1998 Suau, J. M. etal. pigments U.S. Pat. No. 5371180 1994 Groth, T. et al. WO 97/433511997 Krepski, L. R. et al. U.S. Pat. No. 5902357 1999 Riegels, M. et al.dye-levelers U.S. Pat. No. 5902357 1999 Riegels, M. et al. emulsionstabilizers U.S. Pat. No. 5910564 1999 Gruning, B. et al. U.S. Pat. No.6143817 2000 Hallam, M. et. al. fertilizers U.S. Pat. No. 4839461 1989Boehmke, G. fiber treatment agents carpets DE 196 35 061 A1 1998 Groth,T. et al. clothes DE 196 35 061 A1 1998 Groth, T. et al. foaming agentsDE 196 35 061 A1 1998 Groth, T. et al. hair products DE 197 20 771 1998Ferencz, A. et al. flame and fire retardants U.S. Pat. No. 5502251 1996Pohmer, K. et al. flocculents WO 96/08523 1996 Ross, R. J. et al. foaminhibitors U.S. Pat. No. 5401428 1995 Kalota, D. J. et al. foamstabilizers U.S. Pat. No. 5910564 1999 Gruning, B. et al. fungicidesU.S. Pat. No. 5874025 1999 Hewer, L. et al. gas hydrate inhibitors WO96/29502 1996 Duncum, S. et al. gelling materials agricultural uses U.S.Pat. No. 5981761 1999 Chou, Y. et al. fibers U.S. Pat. No. 6027804 2000Chou, Y. et al. films U.S. Pat. No. 5997791 1999 Chou, Y. et al. foodrelated uses U.S. Pat. No. 5981761 1999 Chou, Y. et al. sanitaryarticles U.S. Pat. No. 5773564 1998 Sikes, C. S. U.S. Pat. No. 59555491999 Chang, J. et al. water sealing agents U.S. Pat. No. 5981761 1999Chou, Y. et al. hair curling agents, strengtheners U.S. Pat. No. 59619651999 Kim, S. et al. humectants EP 0 826 716 A2 1998 Nakato, T. and M.Tomida industrial coatings binders U.S. Pat. No. 5597930 1997 Wicks, D.A. et al. removable coatings U.S. Pat. No. 5910532 1999 Schmidt, D. L.and R. D. Mussell smoothing, glossing agents U.S. Pat. No. 6013755 2000Primeaux, D. J. et al. spreading, adhesion agents U.S. Pat. No. 60137552000 Primeaux, D. J. et al. insecticides enhancers U.S. Pat. No. 56461331997 Sanders, J. L. ion exchange resins U.S. Pat. No. 4517241 1985Alpert, A. J. leather auxiliary compounds U.S. Pat. No. 5885474 1999Reiners, J. et al. lipid lowering agents U.S. Pat. No. 5516758 1996Stevens, K. R. and W. V. Taggart lubricants U.S. Pat. No. 6015776 2000Harrison, J. J. and W. R. Ruhe metal cleansing fluids U.S. Pat. No.5443651 1995 Kalota, D. J. and D. C. Silverman metal working fluids U.S.Pat. No. 5401428 1995 Kalota, D. J. et al. U.S. Pat. No. 5616544 1997Kalota, D. J. et al. microbiocides U.S. Pat. No. 5493004 1996 Groth, T.et al. molded materials components JP 10139880 A 1998 Mitsubishi JP10168326 A 1998 Mitsui Toatsu odor control substances U.S. Pat. No.5833972 1998 Wood, L. L. and G. J. Calton oil absorbents U.S. Pat. No.5641847 1997 Hozumi, Y. et al. U.S. Pat. No. 5773564 1998 Sikes, C. S.paper products dewatering agents U.S. Pat. No. 5886095 1999 Bayer, R. etal. strength enhancers U.S. Pat. No. 5902862 1999 Allen, A. J. U.S. Pat.No. 6022449 2000 Jansen, B. et al. suspension agents EP 0860 477 A1 1998Suau, J. M. et al. shampoos and lotions U.S. Pat. No. 5686066 1997Harada, Y. et al. DE 197 20 771 1998 Ferencz, A. et al. surfactants U.S.Pat. No. 6040288 2000 Popoff, C. et al. tartar control U.S. Pat. No.4866161 1989 Sikes, C. S. and A. P. Wheeler U.S. Pat. No. 5266305 1993Wood, L. L. and G. J. Calton thickening agents WO 95/35337 1995 Ross, R.J. et al. U.S. Pat. No. 5773564 1998 Sikes, C. S. tissue-engineeringscaffolding U.S. Pat. No. 5654381 1997 Hrkach, J. S. et al. U.S. Pat.No. 5981467 1999 Hogan, J. C. viscosity modifiers WO 98/34976 1998Martin, D. U.S. Pat. No. 5804639 1998 Schopwinkel, G. et al. U.S. Pat.No. 5886137 1999 Kroner, M. et al.

Preferred but non-limiting uses of the copolymers or the below-discussedderivatives thereof include, use as: detergent, e.g., liquid orpowdered, additives; cosmetic additives, such as softeners oremollients; hair conditioner or shampoo additives; dispersants incementitious materials; active agents in coatings, crosslinkers orbinders; anti-scalants; corrosion inhibitors; adhesives; strengthener orbinder agents for paper products; and gelling or thickening agents.

Derivatization. In addition to the uses as described above, thepolyamino acids of the present invention preferably may be used in thesynthesis of advanced derivatives. That is, advanced derivatives may beprepared via nucleophilic addition of nucleophilic group-containingcompounds, such as amine or —OH group-containing compounds, to the imideresidues of the imide-containing polyamino acids of the presentinvention. These pendant compounds become attached to the polymerbackbone, for example, via amide bonds for the amine compounds or viaester bonds for the —OH group-containing compounds.

Preferably, the derivatization is accomplished in an aqueous solution ofthe imide-containing polyamino acids. Particularly preferred are aqueoussolutions adjusted to the nucleophilic pH range. For example, apreferred pH range is 8 to 12. Particularly preferred is the pH range of10 to 11. The derivatization can be conducted at a wide range oftemperatures with 5 to 90° C., more preferably 20 to 60° C.,particularly 30 to 50° C., being preferred. The amount of succinimideunits derivatized can vary from 1 to all of such units. Somenucleophilic add-ons may be reacted from an emulsion.

Although water is the preferred solvent, organic solvents may be used aswell, particularly in the case in which the imide-containing polyaminoacids are partially or completely insoluble in water. Preferred polarsolvents in these cases are alcohols, particularly isopropanol.Preferred nonpolar solvents are dimethyl formamide, dichloromethane, andparticularly N-methyl-pyrrolidone. In some cases, miscible solutions ofmore than one solvent, including water, may be preferred forderivatization of particular imide-containing polyamino acids.

If the preferred nucleophile itself is not very water-soluble, it may beadded as an emulsion to the solution of the imide-containing polyaminoacid. For example, the hair-conditioning agent,trimethylsilylamodimethicone, is such a water-insoluble nucleophile thatmay be added as an emulsion to the water-soluble, imide-containingpolyamino acid.

Particularly preferred examples of amine compounds for making thederivatives include monoamino polyoxyalkylenes, monoamino siloxanes,monoamino phosphonates, monoamino sulfonates, ethanolamine, and otheramino alcohols. These amine compounds may be added at one imide residueper polymer molecule, at every imide residue per molecule, or at anyother percentage of the imide residues per polymer molecule.

Similarly, amino acids in general also may be added to theimide-containing polymers of the present invention via nucleophilicaddition. For example, preferred additional amino acids to be added viathis approach include: leucine, to provide hydrophobic character;serine, to provide a pendant alcoholic group; dihydroxyphenylalanine, toprovide catecholic character; phosphoserine, to provide a strongeranionic pendant group; alanine, to provide intermediate hydrophobicity,etc. Other amino acids can be added to extend the molecules, for examplepreferably aminocaproic acid and caprolactam. Thus, any and all aminoacids may be added to the imide-containing polyamino acids vianucleophilic addition, for the purposes of adding functional groupcharacteristics ranging from hydrophobic, to nonionic, to anionic, tocationic.

Another preferred embodiment of production of the advanced derivativesis to add OH-containing molecules to the imide residues of theimide-containing polyamino acids via nucleophilic addition under mildlyalkaline aqueous conditions with or without mild heating. These pendantcompounds become attached to the polymer backbone via ester linkages.

Preferred examples of the OH-containing compounds for addition to thepolymer backbones include monomeric carbohydrates and disaccharides suchas glucose, galactose, mannose, lactose, sucrose, and others. Inaddition, polysaccharides such as cellulose, starch, amylose, as well astheir oligosaccharide fragments, may be reacted with theimide-containing polyamino acids.

In each preferred embodiment in which the succinimide residues arederivatized with added functional molecules, it is possible toderivatize all of the succinimide residues per molecule of theimide-containing polyamino acids. It is also possible to derivatize asfew of the succinimide residues per polymer molecule as may be desired,or even less than 1 succinimide residue per molecule, on average. Forexample, it is possible to derivatize from 1% to 100% of the availablesuccinimide residues in a solution of the imide-containing polyaminoacids. Preferably, from 5% to 80% would be derivatized; more preferablyfrom 10% to 60%; most preferably from 20% to 50%.

In addition, it is possible to add the nucleophile derivatizingmolecules to a solution of the imide-containing polyamino acids; oralternatively, it is possible to add the imide-containing polyaminoacids to a solution of the nucleophile derivatizing molecules. Forexample, if there is an excess of nucleophilic amines left free insolution due to a limitation of available succinimide residues forwhatever reason, it is possible to add more of the imide-containingpolyamino acid until all of the nucleophilic amines attach covalently tothe polymer.

The derivatized copolymers are useful in a manner analogous to thecopolymers, as described above, but exhibit the modified propertiesimparted by the added pendant groups.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other features and attendant advantages of the present inventionwill be more fully appreciated as the same becomes better understoodwhen considered in conjunction with the accompanying drawings whereinthe figures depict the following:

FIG. 1. Infrared spectrum of polysuccinimide. Note the characteristicimide peak at ˜1716 cm⁻¹. This polysuccinimide was produced via thermalpolymerization of aspartic acid at 220° C. for 8 hours, yielding acompletely water-insoluble polymer of Mw ˜3000. Note the evidence ofsome degree of ring-opened structure as suggested by the amide peak at1630 cm⁻¹, which is thought to signify branch points, each of whichwould terminate in carboxylic groups. The carboxylic groups are signaledby the peak at 1400 cm⁻¹.

FIG. 2. Infrared spectrum of sodium polyaspartate, prepared by mildalkaline hydrolysis (succinimide ring-opening) of the polysuccinimide ofFIG. 1. This polyaspartate was 11% by weight Na⁺, determined by flamephotometry. Note the characteristic amide doublet at ˜1600 and 1650cm⁻¹, as well as the prominent carboxylate signal at 1400 cm⁻¹.

FIG. 3. Infrared spectrum of L-aspartic acid (zwitterion) prepared byacid precipitation of ammonium aspartate produced via immobilizedenzymatic technology. Note the multiplicity of peaks in the“fingerprint” region between 500 and 1000 cm⁻¹.

FIG. 4. Infrared spectrum of monosodium aspartate. Note the multiplicityof peaks in the “fingerprint” region between 500 and 1000 cm⁻¹.

FIG. 5. Infrared spectrum of L-aspartic acid produced via drying invacuo at 120° C. of a solution of monoammonium aspartate prepared bytitration of L-aspartic acid (zwitterion) of FIG. 3 with ammoniumhydroxide. Note the multiplicity of peaks in the “fingerprint” regionbetween 500 and 1000 cm⁻¹ and the match between this spectrum and thespectrum of FIG. 3.

FIG. 6. Infrared spectrum of a lyophilized, comonomeric preparation ofthe partial sodium salt of the comonomers, aspartic acid (prepared froma solution of ammonium aspartate) and monosodium aspartate, present in a1:1 molar ratio.

FIG. 7. Infrared spectrum of a vacuum-oven-dried (120° C., 50 mm Hg)comonomeric preparation of the present invention: partial sodium salt ofthe comonomers, aspartic acid (prepared from a solution of ammoniumaspartate) and monosodium aspartate, present in the salt in a 1:1 molarratio. Note the peaks in the “fingerprint” region between 500 and 1000cm⁻¹, but also the amide-like peak around 1600 cm⁻¹ and the carboxylatepeak around 1400 cm⁻¹. Notice particularly the differences between thisspectrum, the spectrum of FIG. 6, and the spectra of L-aspartic acid(FIGS. 3 and 5) and monosodium aspartate (FIG. 4).

FIG. 8. Infrared spectrum of the 1:1 copolymer of monosodium aspartateand succinimide, produced via thermal polymerization at 220° C. for 2hours of the monomer preparation of FIG. 6, the 1:1 molar ratio ofmonosodium aspartate and aspartic acid (prepared from a solution ofmonoammonium aspartate). Note the imide signal at ˜1716 cm⁻¹ and theamide signals in the region of 1600 cm⁻¹. Also prominent is thecarboxylate signal at ˜1400 cm⁻¹. Notable by their absence are signalsin the fingerprint region (<1000 cm⁻¹), indicating the absence ofunreacted monomers.

FIG. 9. Infrared spectrum of the 2:1 copolymer of monosodium aspartateand succinimide, produced via thermal polymerization of monosodiumaspartate and monoammonium aspartate at 200° C. for 3 hours. The amidepeaks in the region of 1600 cm⁻¹ became more prominent with increasingrelative amounts of monosodium aspartate monomer. The imide peak at˜1716 cm⁻¹ tended to become accentuated with longer reaction times, asaspartic acid residues were driven more toward the succinimide form.Again, the carboxylate peak at ˜1400 cm⁻¹ is prominent and the monomericpeaks in the fingerprint region (<1000 cm⁻¹) are absent.

FIG. 10. Infrared spectrum of the 1:2 copolymer of monosodium aspartateand succinimide, produced via thermal polymerization of monosodiumaspartate and monoammonium aspartate at 200° C. for 3 hours. In thissample, the imide peak at ˜1716 cm⁻¹ became dominant (also favored bylonger reaction times) because of the increased relative amount ofmonoammonium aspartate monomer, which converts to aspartic acid upondrying, which converts to succinimide upon thermal polycondensation.Although the proportion of residues as aspartate, evidenced by the amidepeaks in the region of 1600 cm⁻¹, was relatively reduced, and theinsoluble imide residues were predominant, the 1:2 copolymer waswater-soluble nonetheless. Also prominent were the carboxylate peak at˜1400 cm⁻¹, and an anhydride doublet at 1213 and 1170 cm⁻¹, whichbecomes increasingly evident with increasing levels of succinimide (atype of anhydride) residues.

FIG. 11. Infrared spectrum of the 3:1 copolymer of monosodium aspartateand succinimide.

FIG. 12. Infrared spectrum of the 1:3 copolymer of monosodium aspartateand succinimide.

FIG. 13. Infrared spectrum of a copolymer of monosodium aspartate andsuccinimide prepared from a 1:1 comonomeric preparation of an intimatecomposition of aspartic acid and sodium bicarbonate.

FIG. 14. Infrared spectrum of a copolymer of monosodium aspartate andsuccinimide prepared from a solution of maleic acid and ammonia in a1:1:1 equivalent ratio plus heat, followed by addition of 0.5 equivalentof sodium hydroxide, followed by drying to form the salt of thecomonomeric preparation.

FIG. 15. Infrared spectrum of L-lysine (free base, zwitterion).

FIG. 16. Infrared spectrum of the 1:1:1 copolymer of monosodiumaspartate, succinimide, and lysine.

FIG. 17. Infrared spectrum of the 1:1:0.5 copolymer of monosodiumaspartate, succinimide, and lysine.

The entire disclosure of all applications, patents and publications,cited above and below, are hereby incorporated by reference.

EXAMPLES

In the foregoing and in the following examples, all temperatures are setforth uncorrected in degrees Celsius.

Infrared Spectroscopy

Infrared spectra of the monomers, the comonomeric preparations, thehomopolymers, and the copolymers were measured by use of an FTIRspectrophotometer (Perkin Elmer, model 1600). Samples were mixed in KBrand 13 mm, disc pellets were made at 9000 lbs. for 3 minutes by use of adie (Spectratech) and press (Carver, Inc.).

Molecular Weight

Molecular weights of polymers were determined by gel permeation.Standards were polyaspartates made in-house by solid-phase methods (ASP₅through Asp₆₀) and commercial polyaspartates (up to 32,000 MW;low-angle, laser light scattering, Sigma Chemical ) and polyglutamates(up to 80,000 MW; low-angle, laser light scattering, Sigma Chemical). Aliquid chromatograph (Varian, model 5500) with a 7.5 mm×30 cm column (G4000 PW, Phenomenex). The mobile phase was 0.01 M Tris, 0.1 M NaCl, pH8.00, flow of 1 ml/mi, UV detection at 235 nm.

Amino Acid Analysis

Confirmation of the composition of the imide-containing polyamino acidsand their derivatives was determined by the PICOTAG protocol (Waters). Asample of 10 μl of a 1 μg/ml stock solution of the polymer washydrolyzed in vacuo at 150° C. for 1 hour in the presence of HCl vaporto yield amine containing monomers. These were derivatized withphenylisothiocyanate and measured by reverse-phase liquid chromatography(Spectraphysics model 8800), 3.9 mm×15 cm column (Waters Division,Millipore, Inc.), acetonitrile gradient, UV detection at 254 mm,detection limit of 10 pmoles per residue.

Alkalimetric Titration of COOH Groups

The relative proportions of aspartate residues and succinimide residuesin the copolymers were also measured via quantitative titration of thecarboxylic groups of the aspartate residues. Samples of approximately100 mg were dissolved or dispersed (if not completely soluble) in 50 mlof water. The pH was adjusted to 2.50 by addition of 1 N HCl, thenimmediately autotitrated to an endpoint of 7.00 with 0.1 N NaOH by useof a computer assisted titrimeter (Fisher Scientific). Comparisons oftheoretical versus actual number of titratable groups per unit weight ofsample of the imide-containing copolymers were made. Control titrationsof homopolymers of polyaspartate and polysuccinimide were used in thecomparisons. The control polymers were made by thermal polycondensationof reagent grade L-aspartic acid (Sigma Chemical) at 220° C. for 8hours. This treatment produced a homopolymer of polysuccinimide asevidenced in the IR spectrum of FIG. 1. Following the ring-openingtreatment by mild alkaline hydrolysis, this polysuccinimide wasconverted to the corresponding sodium polyaspartate as evidenced in theIR spectrum of FIG. 2.

Example 1

Preparation of a comonomeric composition from a 1:1 equivalent solutionof ammonium aspartate and monosodium aspartate, including air-drying at120° C.

An amount of 6.65 g of aspartic acid (0.05 mole, MW 133, Sigma Chemical,L isomer) was slurried with magnetic stirring in 50 ml H₂O in a 600 mlbeaker. An equivalent amount of NH₄OH (32 ml of a 1:10 dilution ofconcentrated ammonium hydroxide, 30% solution, 15.9 M) was added,converting the aspartic acid to monoammonium aspartate in solution. Tothis was added 8.65 g (0.05 mole) of monosodium aspartate (monohydrate,Sigma Chemical), which readily dissolved. The solution was oven-dried inair at 120° C. overnight to form a solid, light yellow but clear, glassypuck.

The beaker containing the puck was rapidly cooled by partial immersionand rotation in a methanol bath to which dry ice was added (temperatureapproaching −30° C.), leading to a clean separation of the puck from theglass. The puck was next fractured manually via mortar and pestle toproduce a granular, glassy product of a comonomeric composition ofsodium aspartate and aspartic acid.

The yield was 15.5 g. This was approximately 1.3% greater thantheoretical (15.3 g) based on the starting amounts of aspartic acid andmonosodium aspartate. The small excess was attributed to residual waterand ammonium ion that remained after the drying step.

Example 2

Preparation of a comonomeric composition from a 1:1 equivalent solutionof ammonium aspartate and monosodium aspartate, including vacuum-dryingat 120° C. The procedures of example 1 were followed except that thedrying step was accomplished in vacuo at a pressure of 50 to 100 mm Hgby use of a vacuum oven set at 120° C. (VWR Scientific, model 1430).

The resulting comonomeric composition of sodium aspartate and asparticacid was obtained in a yield of 15.37 g, which was very close totheoretical (15.3 g), the difference again attributed to residual waterand ammonium ion. In this case, the comonomeric product was colorless,clear, and glassy (for an infrared spectrum, see FIG. 7).

Example 3

Preparation of a comonomeric composition from a 1:1 equivalent solutionof ammonium aspartate and monosodium aspartate by addition of 0.5equivalents of NaOH to a solution of ammonium aspartate, followed byvacuum-drying at 120° C.

An amount of 6.65 g of aspartic acid (0.05 mole, MW 133, Sigma Chemical,L isomer) was slurried with magnetic stirring in 50 ml H₂O in a 600 mlbeaker. An equivalent amount of NH₄OH (32 ml of a 1:10 dilution ofconcentrated ammonium hydroxide, 30% solution, 15.9 M) was added,converting the aspartic acid to monoammonium aspartate in solution. Tothis was added 0.025 mole of NaOH as 2.5 ml of 10 N NaOH. The solutionwas vacuum-dried (50 to 100 mm HG) at 120° C. overnight to form a solid,clear, glassy puck.

The puck was treated as described in example 1 to produce a solid,glassy, fractured, granular comonomeric composition.

Example 4

Preparation of a comonomeric composition from a 1:1 equivalent solutionof ammonium aspartate and monosodium aspartate by addition of 0.5equivalents of NaOH to a solution of ammonium aspartate, prepared frommaleic acid (anhydride) and ammonia, followed by vacuum-drying at 120°C.

In a 250 ml reagent bottle, an amount of 69 ml (0.11 mole) of a 10%solution of concentrated ammonium hydroxide (15.9 M) was slowly addedwith smooth stirring to 9.8 g (0.1 mole) of maleic anhydride in 18 ml (1mole) of water at 60° C. The bottle was capped and the solution allowedto react for 2 hours. The anhydride converted to maleic acid in thepresence of the water, and the ammonia added across the double bond ofmaleic acid to form aspartic acid.

Next, the solution was poured into a 600 ml beaker, then neutralizedwith 0.05 mole of NaOH added as 5 ml of 10 N NaOH to yield a solution ofaspartic acid and sodium aspartate in a 1:1 molar ratio, with a smallexcess of ammonia. Upon vacuum-drying (50 to 100 mm Hg) at 120° C., theammonia was released, leaving the solid, glassy puck of the driedcomposition of the comonomers of the present invention.

The puck was treated as described in example 1 to produce a solid,glassy, fractured, granular comonomeric composition.

Example 5

Preparation of a comonomeric composition from a 1:1:1 equivalentsolution of ammonium aspartate, monosodium aspartate, and lysine,including air-drying at 120° C.

An amount of 3.99 g of aspartic acid (0.03 mole) was slurried withmagnetic stirring in 30 ml H₂O in a 100 ml beaker. An equivalent amountof NH₄OH was added, converting the aspartic acid to monoammoniumaspartate in solution. To this was added 5.19 g (0.03 mole) ofmonosodium aspartate monohydrate, which readily dissolved. Next, 4.926of L-lysine monohydrate (free base, Mw 164.2) was added, which alsodissolved completely. The solution was oven-dried in air at 120° C.overnight to form a solid, light yellow but clear, glassy puck.

The puck was treated as described in example 1 to produce a solid,glassy, fractured, granular comonomeric composition.

Example 6

Preparation of a comonomeric composition from a 1:1:0.6 equivalentsolution of ammonium aspartate, monosodium aspartate, and lysine,including air-drying at 120° C.

The procedure of example 5 was followed except that the lysine was addedas 2.956 g (0.018 mole). This produced a solid comonomeric compositionhaving an equivalent ratio of 1:1:0.6 of aspartate:aspartic acid (fromdrying of soluble ammonium aspartate):lysine.

Example 7

Preparation of a comonomeric composition from a 1:1:0.5 equivalentsolution of ammonium aspartate, monosodium aspartate, and lysine,including air-drying at 120° C.

An amount of 6.65 g of aspartic acid (0.05 mole) was slurried withmagnetic stirring in 50 ml H₂O in a 250 ml beaker. An equivalent amountof NH₄OH was added, converting the aspartic acid to monoammoniumaspartate in solution. To this was added 8.65 g (0.05 mole) ofmonosodium aspartate monohydrate, which readily dissolved. Next, 3.65 gof L-lysine monohydrate (free base, Mw 164.2, 0.025 mole) was added,which also dissolved completely. The solution was oven-dried in air at120° C. overnight to form a solid, light yellow but clear, glassy puck,followed by production of a solid, granular, glassy, pale yellowishcomonomeric composition as above. In this case, the molar ratio ofaspartate:aspartic acid (dried from soluble ammonium aspartate):lysinewas 1:1:0.5.

Example 8

Preparation of a comonomeric composition from a 1:1:0.5 equivalentsolution of ammonium aspartate, monosodium aspartate, and lysine,including lyophilization to form the intimate comonomeric composition asa dried salt.

The procedure of example 7 was followed, except that the solution of thecomonomers was dried by lyophilization to produce a powdery, clear,glassy solid, comonomeric composition.

Example 9

Preparation of a comonomeric composition from a 1:1 solution of asparticacid and lysine, including air-drying at 120° C.

A amount of 6.65 g of aspartic acid (0.05 mole) was slurried in 50 ml ofwater as in example 7. To this was added 8.21 g (0.05 mole) of lysinefree base, which itself acted to neutralize the aspartic acid, bringingit into solution, without the need for addition of ammonium hydroxide.This solution was dried at 120° C. in air, producing a clear, yellowish,glassy puck. This then was treated as above to yield a solid, granular,glassy comonomeric composition of aspartate and lysine. As shown below,e.g., see Example 21, polymerization of such comonomeric compositionresulted in a product which was not water-soluble.

Example 10

Thermal polymerization of the 1:1 equivalent comonomeric compositionprepared from the solution of monosodium aspartate and monoammoniumaspartate to produce a copolymer of sodium aspartate and succinimide bythermal treatment at 220° C.

The comonomeric composition of example 1 was prepared as follows. Anamount of 6.65 g of aspartic acid (0.05 mole, MW 133, Sigma Chemical, Lisomer) was slurried with magnetic stirring in 50 ml H₂O in a 600 mlbeaker. An equivalent amount of NH₄OH (32 ml of a 1:10 dilution ofconcentrated ammonium hydroxide, 30% solution, 15.9 M) was added,converting the aspartic acid to monoammonium aspartate in solution. Tothis was added 8.65 g (0.05 mole) of monosodium aspartate (monohydrate,Sigma Chemical), which readily dissolved. The solution was oven-dried at120° C. overnight to form a comonomeric composition in the form of asolid, clear, glassy puck.

The material was next thermally polymerized at 220° C. for 2 hours in avacuum oven at a pressure of 50 mm of Hg. During this treatment, theglassy puck of the intimate salt of aspartic acid and monosodiumaspartate initially boiled for a few moments, driving off residual waterof solution, then as the temperature of the material equilibrated withthe ambient temperature of the oven, the polymerization began. This wasaccompanied by a rising of the mass as the water of condensationevolved. The material, being ionic and moist at first, was sticky andwas carried upward as the water was driven off. The material can bebriefly retrieved from the oven and manually pushed downward into thebeaker, keeping track of the time at temperature, or the vacuum may bereleased from time to time to promote the collapse of the rising mass.

The material hardens after approximately 1 hour of reaction, no longerbeing moist, at which point, it can be packed manually into the reactionvessel. Or it may be left as is, in a somewhat foamed condition,allowing the reaction to proceed to completion over the next hour at220° C.

The product polymer was beige in color. The yield was 11.3 g. The GPCmolecular weight (number average) was 1200. The material was readilysoluble in water. It was also soluble to a lesser extent in 50%isopropanol in water. The infrared spectrum (FIG. 8) revealed a mixedamide/imide structure (aspartate/succinimide) in a 1:1 residue ratio.

The yield of product copolymer of aspartate and succinimide at 11.3 gwas 73% of the total amount of reactant monomers (15.3 g). This wasequivalent to 97% of theoretical yield, which was calculated on thebasis of loss of weight upon conversion of aspartic acid (133 g/mol) tosuccinimide residues (97 g/mol-residue) and the loss of weight uponconversion of monosodium aspartate monohydrate (173 g/mol) to sodiumaspartate residues (137 g/mol-residue). That is, 100% theoretical yieldof conversion of aspartic acid to polysuccinimide is 0.729 of the amountof monomer reactant: 100% conversion of monosodium aspartate monohydrateto poly(monosodium aspartate) is 0.792 of the amount of the monomerreactant. Accordingly, 100% theoretical yield of conversion of a 1:1monomer composition of aspartic acid and monosodium aspartatemonohydrate to copoly(aspartate, succinimide) 1:1 is 0.761 of the amountof the monomer mixture.

In the following examples 11-28, the yields of products in every casefell within the range of 0.70 to 0.80 of the combined amounts of themonomer reactants. This suggested that the reactions occurredefficiently, with yields at or near theoretical.

Example 11

Thermal polymerization of the 1:1 equivalent comonomeric compositionprepared from the solution of monosodium aspartate and monoammoniumaspartate to produce a copolymer of sodium aspartate and succinimide bythermal treatment at 180° C.

The comonomeric composition of example 10 was thermally polymerized at180° C. for 4 hours in a vacuum oven at a pressure of 50 mm of Hg. Thereaction proceeded during this treatment as described above in example10, although somewhat slower, producing a light sandstone-coloredmaterial.

The yield of product copolymer of aspartate and succinimide at 11.34 gwas 73.8% of the total amount of reactant monomers (15.37 g). This wasequivalent to 97% of theoretical yield, which as explained above, forthe 1:1 copolymer, is 0.761 of the amount of the monomer mixture.

Example 12

Thermal polymerization of the comonomeric composition prepared from thesolution of monosodium aspartate and monoammonium aspartate in a 2:1monomer ratio at 200° C.

The procedures of example 10 were followed, with adjustments as follows.In preparing the comonomeric composition, the amount of aspartic acidwas 3.991 g (0.03 mole). The amount of monosodium aspartate monohydratewas 10.38 g (0.06 mole).

The comonomeric salts were polymerized at 200° C. The reaction wasallowed to proceed to completion for 3 hours. The GPC Mw of the productwas 1000. The IR spectrum (FIG. 9) revealed the presence of residues ofaspartate and succinimide in a 2:1 monomer ratio. The product was lightyellow-orange in color and very soluble in water.

Example 13

Thermal polymerization of the comonomeric composition prepared from thesolution of monosodium aspartate and monoammonium aspartate in a 1:2monomer ratio at 200° C.

The procedures of example 12 were followed, except reversing the molaramounts of the reactant monomers. That is, the amount of monosodiumaspartate monohydrate was 5.19 g (0.03 mole) and the amount of asparticacid was 7.98 g (0.06 mole). The GPC Mw of the product was 1000. The IRspectrum (FIG. 10) revealed the presence of residues of aspartate andsuccinimide in a 1:2 monomer ratio. The product was soluble in water.

Example 14

Thermal polymerization of the comonomeric composition prepared from thesolution of monosodium aspartate and monoammonium aspartate in a 3:1monomer ratio at 200° C. for 4 h without vacuum.

The procedures of example 12 were followed, except that the molaramounts of the reactant monomers were changed. That is, the amount ofmonosodium aspartate monohydrate was 10.38 g (0.06 mole) and the amountof aspartic acid was 2.66 g (0.02 mole). The GPC Mw was 1500. The IRspectrum (FIG. 11) revealed the presence of residues of aspartate andsuccinimide in a 3:1 monomer ratio. The product was very soluble inwater, but was somewhat darker in color, although still a light tan, ascompared to products prepared in partial vacuums.

Example 15

Thermal polymerization of the comonomeric composition prepared from thesolution of monosodium aspartate and monoammonium aspartate in a 1:3monomer ratio at 200° C. for 4 h without vacuum.

The procedures of example 14 were followed, except that the molar ratioof the reactant monomers was reversed. That is, the amount of monosodiumaspartate monohydrate was 4.325 g (0.025 mole) and the amount ofaspartic acid was 9.975 g (0.075 mole). The GPC Mw was 1800. The IRspectrum (FIG. 12) revealed the presence of residues of aspartate andsuccinimide in a 1:3 monomer ratio. The product was soluble in water,again with a somewhat darker tan color than products prepared in partialvacuums.

Example 16

Thermal polymerization of the comonomeric composition prepared from asolution of monosodium aspartate and monoammonium aspartate in a 4:1monomer ratio at 200° C. for 4 h.

The procedures of example 14 were followed, except that the molar ratioof the reactant monomers was changed. That is, the amount of monosodiumaspartate monohydrate was 3.46 g (0.02 mole) and the amount of asparticacid was 0.665 g (0.005 mole), prepared as a slurry in 10 ml of water ina 50 ml beaker, then treated with 3.2 ml of the NH₄OH solution (1.59 M,a 1:10 dilution of the 30% stock solution). The GPC Mw was 1200. The IRspectrum (not shown) revealed the presence of residues of aspartate andsuccinimide in a 4:1 monomer ratio. The product was soluble in water,with an orange-brownish color.

Example 17

Thermal polymerization of the comonomeric composition prepared from asolution of monosodium aspartate and monoammonium aspartate in a 1:4monomer ratio at 200° C. for 4 h.

The procedures of example 16 were followed except that the ratio ofmonomer reactants was reversed. That is, the amount of monosodiumaspartate monohydrate was 1.038 g (0.006 mole) and the amount ofaspartic acid was 3.192 g (0.024 mole). The GPC Mw was 1200. The IRspectrum (not shown) revealed the presence of residues of aspartate andsuccinimide in a 1:4 monomer ratio. The product retained significantsolubility in water, even with an elevated succinimide content, and wasan orange-brownish color.

Example 18

Thermal polymerization of an intimate admixture of aspartic acid andsodium bicarbonate in a 1:1 equivalent ratio at 220° C.

The water of condensation creates a vapor phase during thepolymerization of aspartic acid. In the presence of sodium bicarbonate,bicarbonate anion can enter a transitory aqueous state, with sodiumcation also solubilized momentarily. The bicarbonate decomposes in thepresence of heat and water vapor to release CO₂ and water, furtherstirring the admixture through gaseous emission. The sodium can become acounterion to some of the aspartic residues in the form of monosodiumaspartate, thus generating an intimate mixture of aspartic acid andmonosodium aspartate. Upon thermal polymerization, this intimate mixtureconverts to the copolymer of aspartate and succinimide.

An amount of 6.65 g of aspartic acid (0.05 mole, MW 133, Sigma Chemical,L isomer) was pulverized with 4.2 g of NaHCO₃ by mortar and pestle, thenplaced in a 600 ml beaker. The intimate admixture was polymerized at220° C. for 3 hours in a vacuum oven at a pressure of 50 mm of Hg.

The IR spectrum (FIG. 13) of the product revealed the presence of bothaspartate and succinimide residues.

Example 19

Thermal polymerization of the comonomeric composition prepared from asolution of maleic acid, ammonia, and a nonalkaline salt of sodiumsulfate at 200° C.

In a 250 ml reagent bottle, an amount of 69 ml (0.11 mole) of a 10%solution of concentrated ammonium hydroxide (15.9 M) was slowly addedwith smooth stirring to 9.8 g (0.1 mole) of maleic anhydride in 18 ml (1mole) of water at 60° C. The bottle was capped and the solution allowedto react for 2 hours. Next, 0.025 mole (3.55 g) of Na₂SO₄ (Mw 142) wasadded as 14.2 ml of a 25% by weight aqueous solution. The solution waspoured into a 1 liter beaker and dried overnight at 120° C. to form ahardened puck, then polymerized at 200° C. for 2 hours.

The IR spectrum of the product polymer revealed the presence of bothaspartate and succinimide residues.

Example 20

Thermal polymerization of the comonomeric composition prepared from asolution of maleic acid and ammonia, plus NaOH, at 200° C.

The procedures of example 19 were followed except that the solution ofmaleic, ammonia, and water was treated with 0.05 mole of NaOH added as 5ml of 10 N NaOH, rather than by addition of sodium sulfate. The IRspectrum (FIG. 14) of the product polymer revealed the presence of bothaspartate and succinimide residues.

Example 21

Thermal polymerization of the comonomeric composition prepared from asolution of monoammonium aspartate and lysine in a 1:1 monomer ratio at180° C.

An amount of 6.65 g of aspartic acid (0.05 mole, MW 133, Sigma Chemical,L isomer) was slurried with magnetic stirring in 50 ml H₂O in a 1 literbeaker. An equivalent amount of NH₄OH (32 ml of a 1:10 dilution ofconcentrated ammonium hydroxide, 30% solution, 15.9 M) was added,dissolving the aspartic acid and converting it to monoammonium aspartatein solution. To this was added 7.31g (0.05 mole) of lysine (free base,Mw 146.2, Sigma Chemical, L-isomer: see the IR spectrum of FIG. 15),which readily dissolved. The solution was oven-dried at 120° C.overnight to form a solid, light amber, glassy puck.

The material was polymerized at 180° C. for 3 hours in a vacuum oven at50 mm of Hg. The water of condensation was vented occasionally byreleasing the vacuum, which resulted in a collapse of the rising mass ofthe condensate.

The product polymer was insoluble in water, presumably due tocrosslinking via lysine residues. The IR spectrum revealed the presenceof imide residues.

Example 22

Thermal polymerization of a comonomeric composition prepared from asolution of aspartic acid and lysine in a 1:1 monomer ratio at 180° C.

The procedures of example 21 were followed except that the aspartic acidslurry was not neutralized with ammonium hydroxide. Rather the lysineitself served to neutralize and solubilize the aspartic acid.

The product polymer was insoluble in water. The IR spectrum revealed thepresence of imide residues.

Example 23

Thermal polymerization of a comonomeric composition prepared from asolution of monosodium glutamate and monoammonium aspartate in a 1:1monomer ratio at 220° C.

Glutamic acid often is regarded as an inefficiently polymerizablemonomer because it forms a melt of a cyclic pyroglutamic condensate ofitself upon heating, thus removing its amine group and one carboxylicgroup from further chain lengthening, condensation bonds. However,addition of sodium to block the cyclizing reaction can promoteincorporation of monosodium glutamate into polyamino acids. By formingan intimate, dry composition of aspartic acid (dried from ammoniumaspartate in solution) and monosodium glutamate, it is possible tocondense these monomers into a polymer of succinimide and monosodiumglutamate.

An amount of 6.65 g of aspartic acid (0.05 mole, MW 133, Sigma Chemical,L isomer) was slurried with magnetic stirring in 50 ml H₂O in a 1 literbeaker. An equivalent amount of NH₄OH (32 ml of a 1:10 dilution ofconcentrated ammonium hydroxide, 30% solution, 15.9 M) was added,dissolving the aspartic acid and converting it to monoammonium aspartatein solution. To this was added 9.35 g (0.05 mole) of monosodiumglutamate (monohydrate, Mw 187, Sigma Chemical, L-isomer), which readilydissolved. The solution was oven-dried at 120° C. overnight to form asolid, clear, glassy puck.

The material was next thermally polymerized at 220° C. for 2 hours in avacuum oven at a pressure of 50 mm of Hg. During this treatment, theglassy puck of the intimate composition of sodium salts of aspartate andglutamate, along with their acid forms, initially boiled for a fewmoments, driving off residual water of solution, then as the temperatureof the material equilibrated with the ambient temperature of the oven,the polymerization began. This rising mass of the condensate wascollapsed from time to time by venting the vacuum.

A water-soluble polymer was produced. The IR spectrum (not shown)revealed the presence of imide residues.

Example 24

Thermal polymerization of a comonomeric composition prepared from asolution of aspartic acid, monosodium glutamate, and lysine in a 1:1:1monomer ratio at 220° C.

Terpolymers and polymers with more complex mixtures of monomers can alsobe produced that contain imide residues.

An amount of 6.65 g of aspartic acid (0.05 mole, MW 133, Sigma Chemical,L isomer) was slurried with magnetic stirring in 50 ml H₂O in a 1 literbeaker. To this was added 7.31 g (0.05 mole) of lysine (free base, Mw146.2, Sigma Chemical, L-isomer), which was readily dissolved and alsoneutralized and solubilized the aspartic acid. Next, 9.35 g (0.05 mole)of monosodium glutamate (monohydrate, Mw 187, Sigma Chemical, L-isomer)was added, which also readily dissolved. The solution was oven-dried at120° C. overnight to form a solid, light amber, glassy puck.

The material was next thermally polymerized at 220° C. for 2 hours in avacuum oven at a pressure of 50 mm of Hg. The rising mass of thecondensate was collapsed from time to time during the first hour byventing the vacuum.

The IR spectrum (not shown) of the product polymer revealed the presenceof imide residues. The imide-containing polyamino acid was insoluble inwater.

Example 25

Thermal polymerization of a comonomeric composition prepared from asolution of monosodium aspartate, ammonium aspartate, and lysine in a1:1:1 monomer ratio at 200° C. for 4 h in a partial vacuum.

The comonomeric composition of example 5 was polymerized in a vacuumoven at a pressure of 50 mm Hg for 4 h at 200° C. The IR spectrum (FIG.16) of the product material revealed the presence of imide residues. Thematerial was insoluble in water, even at 1 mg/ml, but was somewhatgelled. Upon mild alkaline ring-opening of the imide residues at pH 10,60° C. for 1 to 2 h, the material remained insoluble at 1 mg/ml, butincreased in the amount of its gelling properties.

The polymeric material presumably is crosslinked via the lysineresidues, forming a continuous network that interacts readily with waterbut is too large to be solubilized. Thus the Mw of the polymericmaterial is very high, although not assignable exactly, with eachparticle possibly equivalent to a continuous, covalently linked“molecule”.

Example 26

Thermal polymerization of a comonomeric composition prepared from asolution of monosodium aspartate, ammonium aspartate, and lysine in a1:1:0.6 monomer ratio at 200° C. for 4 h in a partial vacuum.

The comonomeric composition of example 6 was polymerized according tothe procedures of example 25. As described in example 25, the productmaterial was an imide-containing polyamino acid that had gellingproperties, but was largely water-insoluble. Upon the ring-openingtreatment, the material increased in its gelling properties, renderingthe solution at 1 mg/ml partially gelled and noticeably viscous.

Example 27

Thermal polymerization of a comonomeric composition prepared from asolution of monosodium aspartate, ammonium aspartate, and lysine in a1:1:0.5 monomer ratio at 200° C. for 4 h in a partial vacuum.

The comonomeric composition of example 7 (oven-dried at 120° C.) waspolymerized according to the procedures of example 25. Again, the IRspectrum (FIG. 17) of the polymer product revealed the presence of imideresidues. In this case, the material was mostly soluble in water at 1mg/ml. The GPC Mw of the soluble fraction of the imide-containingpolyamino acid was 1500. A lesser fraction of the material formed aviscous, loose, aqueous gel.

Example 28

Thermal polymerization of a lyophilized comonomeric composition preparedfrom a solution of monosodium aspartate, ammonium aspartate, and lysinein a 1:1:0.5 monomer ratio at 200° C. for 4 h in a partial vacuum.

The comonomeric composition of example 8 was polymerized according tothe procedures of example 27, except that the dry, intimate compositionof monosodium aspartate, aspartic acid (dried from ammonium aspartate insolution), and lysine was prepared by lyophilization rather thanoven-drying at 120° C. The product material was very similar to thematerial of example 27, indicating that the drying step via boilingduring preparation of the comonomeric composition did not adverselyaffect the comonomeric preparation.

The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexamples.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

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We claim:
 1. A method for preparing a mixture of aspartic acid and asalt of aspartic acid which comprises: drying a solution of a salt ofaspartic acid having a cation which does not volatilize during thedrying and a salt of aspartic acid having a cation which at leastpartially volatilizes to provide free aspartic acid during the drying.2. The method of claim 1, which is conducted in the substantial absenceof anions other than aspartic acid ions and OH⁻ ions.
 3. The method ofclaim 1, wherein the salt of aspartic acid having a cation which doesnot volatilize is an alkali metal or alkaline earth metal salt and thesalt of aspartic acid having a cation which at least partiallyvolatilizes is an ammonium or amine salt.
 4. The method of claim 1,wherein the salt of aspartic acid having a cation which does notvolatilize is a sodium salt and the salt of aspartic acid having acation which at least partially volatilizes is an ammonium salt.
 5. Themethod of claim 1, wherein at least 95% by weight of the salt ofaspartic acid having a cation which at least partially volatilizes isvolatilized to free aspartic acid during the drying.
 6. A mixture ofaspartic acid and a salt of aspartic acid prepared by the method ofclaim
 1. 7. The mixture of claim 6, wherein the salt of aspartic acid isa sodium salt.
 8. A mixture of aspartic acid and a salt of aspartic acidwhich comprises free aspartic acid and a salt of aspartic acid having acation which does not volatilize in a molar ratio of 1:4 to 4:1.
 9. Amixture of aspartic acid and a salt of aspartic acid of claim 8 whichcomprises free aspartic acid and the salt of aspartic acid approximatelyin a molar ratio of 1:1.
 10. A mixture of claim 8, which additionallycomprises up to 2% by weight of an ammonia or amine salt of asparticacid.
 11. A mixture of claim 8, wherein the salt of aspartic acid havinga cation which does not volatilize is a sodium salt.
 12. A solution of asalt of aspartic acid having a non-volatilizable cation and a salt ofaspartic acid having a volatilizable cation.
 13. The solution of claim12, wherein the salt of aspartic acid having a non-volatilizable cationis an alkali metal or alkaline earth metal salt and the salt of asparticacid having a volatilizable cation is an ammonium or amine salt.
 14. Thesolution of claim 12, wherein the salt of aspartic acid having anon-volatilizable cation is a sodium salt and the salt of aspartic acidhaving a volatilizable cation is an ammonium salt.
 15. The solution ofclaim 12 wherein the salt of aspartic acid having a non-volatilizableand the salt of aspartic acid having a volatilizable are present in amolar ratio of 1:10 to 10:1.
 16. The solution of claim 12 wherein thesalt of aspartic acid having a non-volatilizable cation and the salt ofaspartic acid having a volatilizable are present in a molar ratio of 1:4to 4:1.
 17. A mixture of aspartic acid and a salt of aspartic acidprepared by drying a solution according to claim
 12. 18. A mixture ofaspartic acid and a salt of aspartic acid prepared by drying a solutionaccording to claim
 13. 19. A mixture of an acid salt of aspartic acidand aspartic acid wherein positively charged amino groups of theaspartic acid molecules are balanced substantially only by saltformation with other aspartic acid molecules or with the anions of saidacid salt of aspartic acid.
 20. The mixture of claim 19, wherein theacid salt is a sodium salt.
 21. The method of claim 1, wherein saidsolution comprises an additional comonomer useful for copolymerizingwith the aspartic acid and salt of aspartic acid.
 22. The method ofclaim 21, wherein the additional comonomer is a compound containing atleast two amino groups.
 23. The method of claim 21, wherein theadditional comonomer is glutamic acid, a glutamate, lysine, aminocaproicacid, diaminohexane, diaminobutane or diaminopentane.
 24. The mixture ofclaim 6, wherein said solution comprises an additional comonomer usefulfor copolymerizing with the aspartic acid and salt of aspartic acid. 25.The mixture of claim 24, wherein the additional comonomer is a compoundcontaining at least two amino groups.
 26. The mixture of claim 24,wherein the additional comonomer is glutamic acid, a glutamate, lysine,aminocaproic acid, diaminohexane, diaminobutane or diaminopentane. 27.The solution of claim 12, salt wherein the ammonium salt is prepared viaan immobilized enzyme or soluble enzyme method, and to which sodiumaspartate is added or which is titrated with NaOH to provide the sodiumsalt.
 28. The solution of claim 12, wherein the salt of aspartic acidhaving a non-volatilizable cation is a sodium salt and the salt ofaspartic acid having a volatilizable cation is an ammonium salt whereinthe ammonium salt is prepared via a chemical method, and to which sodiumaspartate is added or which is titrated with NaOH to provide the sodiumsalt.
 29. The method of claim 1, wherein the drying is conducted byheating, applying a vacuum, lyophilizing, spray drying, forced airdrying or a combination thereof.
 30. The method of claim 1, wherein thedrying is conducted by heating.
 31. A method for preparing a copolymercontaining copolymerized aspartate units and succinimide units whichcomprises: heating to polymerize a comonomer mixture of aspartic acidand a salt of aspartic acid, which comonomer mixture was prepared bydrying a solution of a salt of aspartic acid having a cation which doesnot volatilize during the drying and a salt of aspartic acid having acation which at least partially volatilizes to free aspartic acid duringthe drying.
 32. The method of claim 31, wherein at least 95% by weightof the cation of the salt having a cation which at least partiallyvolatilizes to free aspartic acid during the drying does volatilize. 33.The method of claim 31, wherein the resulting copolymer containsaspartate units and succinimide units in a molar ratio of from 1:10 to10:1.
 34. A copolymer containing copolymerized aspartate units andsuccinimide units prepared by the method of claim 31 or a derivative ofthis copolymer derivatized by reacting an amino group-containingcompound, —OH group-containing compound or other nucleophilicgroup-containing compound with at least one succinimide unit of thecopolymer.
 35. A copolymer containing copolymerized aspartate units andsuccinimide units in a ratio of from 1:4 to 4:1 or a derivative of thiscopolymer derivatized by reacting an amino group-containing compound,—OH group-containing compound or other nucleophilic group-containingcompound with at least one succinimide unit of the copolymer.
 36. Themethod of claim 31, wherein an additional comonomer is provided in thecomonomer mixture.
 37. The method of claim 36, wherein the additionalcomonomer is a compound containing at least two amino groups.
 38. Themethod of claim 36, wherein the additional comonomer is glutamic acid, aglutamate, lysine, aminocaproic acid, diaminohexane, diaminobutane ordiaminopentane.
 39. The copolymer of claim 34, which comprises anadditional comonomer unit.
 40. The copolymer of claim 39, wherein theadditional comonomer is from a compound containing at least two aminogroups.
 41. The copolymer of claim 39, wherein the additional comonomeris from glutamic acid, a glutamate, lysine, aminocaproic acid,diaminohexane, diaminobutane or diaminopentane.
 42. The method of claim31, wherein the drying is conducted by heating, applying a vacuum,lyophilizing, spray drying, forced air drying or a combination thereof.43. The method of claim 31, wherein the drying is conducted by heating.44. A method of using a copolymer of claim 34, wherein water solubilityof the copolymer is provided to effect such use.
 45. A composition foruse in a method requiring a polymer material wherein the compositioncomprises a copolymer of claim 34 and an adjuvant acceptable to suchuse.
 46. A composition of claim 45, wherein the composition is anadhesive.
 47. A composition for use in a method requiring a polymermaterial wherein the composition comprises a copolymer of claim 35 andan adjuvant acceptable to such use.
 48. A method for treating hair orfibers which comprises applying a composition comprising a copolymer ofclaim 34 thereto.
 49. The method of claim 48, wherein the composition isa shampoo or hair conditioner.
 50. A method for water treatment whichcomprises using a copolymer of claim 34 as a flocculent, antiscalant,corrosion inhibitor or dispersant in the method.
 51. A method forapplying a coating to an object, wherein the coating comprises acopolymer of claim
 34. 52. A method for preparing a detergentcomposition which comprises incorporating a copolymer of claim 34therein.
 53. The method of claim 52, wherein the detergent compositionprepared is a liquid laundry detergent composition.
 54. A method forpreparing a cosmetic which comprises incorporating a copolymer of claim34 therein.
 55. The method of claim 54, wherein the cosmetic prepared isa skin or hair lotion.
 56. A method for preparing a cementitiousmaterial which comprises incorporating a copolymer of claim 34 therein.57. A method for reducing scaling in a water-containing compositionwhich comprises incorporating a copolymer of claim 34 as an anti-scalantin the composition.
 58. A method for reducing corrosion on a surfacewhich comprises treating the surface with a composition comprising acopolymer of claim
 34. 59. A method for preparing a paper product whichcomprises incorporating a copolymer of claim 34 as a strengthener orbinder therein.
 60. A superabsorbent material which comprises acopolymer of claim
 34. 61. A superabsorbent material of claim 60 whichis in the form of a disposable diaper, incontinence article or bandage.62. A method for gelling or thickening a composition which comprisesincorporating a copolymer of claim 34 therein.
 63. A method formodifying the viscosity of a composition which comprises incorporating acopolymer of claim 34 therein.
 64. A copolymer containing copolymerizedaspartate units and succinimide units in a ratio of from 1:10 to 10:1 ora derivative of this copolymer derivatized by reacting an aminogroup-containing compound, —OH group-containing compound or othernucleophilic group-containing compound with at least one succinimideunit of the copolymer; provided that the copolymer is not a copolymerresulting from a process of adjusting the pH of a solution of asparticacid with sodium hydroxide to a pH of from 3-7, drying the solution to asolid and then heating the solid to polymerize.
 65. A copolymercontaining copolymerized aspartate units and succinimide units in aratio of from 1:10 to 10:1 or a derivative of this copolymer derivatizedby reacting an amino group-containing compound, —OH group-containingcompound or other nucleophilic group-containing compound with at leastone succinimide unit of the copolymer; wherein the copolymer is inisolated form.